I am developing an embedded system and attaching a uSD-card to it in SD mode (not SPI). The requirement is such that I have to switch the uSD card connectivity between two ports so I am using 74HC4053 as a switch. I have verified all the connections and they are fine. Now when I plug my uSD card and attach one of the ports to a uSD-card reader, the card never responds. Even though I can see that CMD and CLK signals are reaching the uSD card all fine, the card never responds to the commands on the data lines. Any idea what can be going wrong here?

In the same configuration, I used TI's CD4053 (which is lower speed than the CMOS based 74HC4053) and it works fine. I wonder what can be the problem in my circuit. The only intriguing thing I can see in the datasheets of CD4053 and 74HC4053 is that the former has a much lower rON ~5 ohm while the later has ~50 ohm.

Below is a simplified connection diagramenter image description here

  • \$\begingroup\$ do you have termination resistors close to your host, by any chance? What resistance do your SD bus pull up resistors have? \$\endgroup\$ – Marcus Müller Jan 16 at 14:35
  • \$\begingroup\$ Thanks for the response. I haven't put any resistors. Its just that instead of directly plugging the uSD card to the card reader, I am using a 74HC4053 in between. \$\endgroup\$ – UmairKhan Jan 16 at 14:45

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